Cascading dropdown based on other list

Hi Guys,

I need some help with cascading dropdown list in PowerApps.

I have 3 lists:

• NewEmployeeForm_Departments
  where I have only one Title column with departments description
• NewEmployeeForm_Positions
  where I have one title column with job positions description and one lookup column connected with departments list
• NewEmployeeForm
  many different columns and two lookup columns connected to departments and positions lists

I've prepared PowerApps form to third list, but unfortunately I'm not able to filter positions based on departments.

I tried two following scenarios:

1. 
   Department

   Choices(NewEmployeeForm.Department)

   Position

   Sort(Distinct(Filter(NewEmployeeForm_Positions;Department=DataCardValue2.Selected.Value);Title);Result)

   
   And this works fine - filter works. Unfortunately when I submitting the form Position column is empty. And it makes sense, because I am referring to the different list (NewEmployeeForm_Positions)
2. 
   Department

   Choices(NewEmployeeForm.Department)

   Position
   I tried with something like below, but probably it isn't good approach:

   Filter(Choices(NewEmployeeForm.Position);Department.Value=DataCardValue2.Selected.Value in NewEmployeeForm_Positions.Department)

   
   Could you Guys point me to correct way to achive that goal?
   Many thanks.